1. Field of Invention
This invention relates to lifting and hoisting fittings used by mechanics.
2. Description of Prior Art
The lifting and hoisting of heavy objects by machinists and mechanics are often facilitated by the useof a lifting fitting which is screwed into a threaded receiving hole located on the object to be lifted. Lifting fittings are designed to provide a surface of suitable dimension and strength for engagement and subsequent hoisting by a lifting hook, chain, cable, or the like. The most common lifting fitting is the so-called lifting eye which consists of a metal ring having a single radially extending threaded stud. These lifting eyes are found in everyday use in machine shops, auto repair shops, and other repair and maintenance facilities which share the need for lifting and moving heavy mechanical objects.
Engine blocks, large electric generators, and other heavy mechanical objects frequently have threaded holes suitable for receiving the threaded stud of a lifting eye. It is generally found that the majority of the objects lifted have holes which are threaded in one of four or five common thread sizes. The mechanic must, therefore, have on hand an assortment of lifting eyes in order to fit the usual variety of mechanical objects which are encountered in his work.
Much time is wasted in selecting and fitting lifting eyes to objects. Often the eye of the proper size is lost or misplaced. Heavy-duty lifting eyes are frequently of sufficient size and weight to preclude a person from carrying more than one or two at a time. If the proper size thread is not chosen on the first try, the mechanic must go back to the toolbox to obtain an eye of the proper size. The necessity of selecting, in advance, a lifting eye of the proper thread size for connection to the object to be lifted wastes time and creates storage problems. Additionally, given the fact that a mechanic generally uses one eye at a time, it is wasteful to have a toolbox full of idle lifting eyes which differ from the one in use only in the thread size of the attached stud.
If a single lifting device could be fitted to objects having various sizes of threaded receptacles, then the delays, waste, and duplication attendant to storage, selection, and use of common lifting eyes would be eliminated. Accordingly, there is a need for a lifting device which can be fitted to a variety of threaded receptacles without impairing the ability of the device to receive a hook, chain, cable or other lifting means.